Washing machines typically include a cabinet that receives a tub for containing wash and rinse water. A wash basket is rotatably mounted within the wash tub. A drive assembly and a brake assembly can be positioned with respect to the wash tub and configured to rotate and control the rotation of the wash basket within the wash tub to cleanse the wash load loaded into the wash basket. During a wash cycle, water is typically extracted from the wash load by revolving the wash basket containing the wash load at a high rotational velocity. Centrifugal forces pull the majority of the water out of the wash load and through perforations in the rotating basket. A pump assembly can be used to rinse and drain the extracted water to a draining system.
The rotating basket and wash tub are typically supported by a suspension system designed to dampen translational motion induced by any imbalance within the rotating basket. High stresses are sometimes encountered within the basket, drive system, and suspension system during the high-speed spin action used for water extraction during normal wash cycles. An out of balance mass in the wash load during a high-speed spin cycle can generate significant forces, leading to damage to the washer. For instance, with an imbalance within the wash load, a force is generated which is proportional to the product of the mass, the distance between the imbalance and the center of rotation, and the square of the velocity. Continued spin operation with an out of balance load causes unnecessary wear and tear on mechanical and electrical components in the washer and reduces the reliability of the product over time.
It is known to detect out of balance conditions of a washing machine using dedicated sensors, such as mechanical limit switches to detect tub strikes during an out of balance condition. As used herein, a tub strike is contact between the wash tub and the cabinet while the wash basket is spinning in within the wash tub. Other methods and systems monitor the power and energy that is consumed by the washing machine motor under various operating conditions.
While various methods for detecting an out of balance condition of a washing machine are known, a need exists for an improved method of detecting an out of balance condition of a washing machine. A method that can be performed by the existing inverter drive control system for the washing machine would be particularly useful.